Patent GB-1425488-A (GB)
Title: Combined gas and steam power plants
IPC: F01D21/02
Filed: 1973-05-07
Abstract: 1425488 Steam and gas turbine power plant SULZER BROS Ltd 7 May 1973 [9 May 1972 17 July 1972] 21682/73 Headings F1G and F1Q A combined steam and gas turbine power plant comprises a steam generator 5, a steam turbine 24 driving an electric generator 25, and a gas turbine 11 driving an air compressor 16 and an electric generator 15. The steam generator has evaporator and super-heat sections 6, 7 from which steam is supplied to the turbine 24 through line 23, condensate returning to the evaporator section through line 26. Air under pressure from the compressor 16 passes through line 2 to the combustion section of the steam generator, fuel also being supplied thereto through line 4. Combustion gases discharge from the combustion section through line 10 to the gas turbine 11 then discharge to atmosphere. Means are provided for supplying water into the air passing to the combustion section or into the gases discharging from the combustion section so as to reduce the power of the gas turbine upon loss or reduction of load on the electric generator 15 so as to prevent overspeeding of the assembly, the means comprising an injector 32 disposed in the compressed air line 2 and supp supplied with water from the feed water line 26, the supply being controlled by a valve 31. The load on the generator 15 is sensed by an ammeter 37 a signal from which is passed through a device 36 with derivative action to an actuator 35 which controls the valve 31 and thus the supply of water to the injector 32. In Fig. 3 the load on the governor is sensed by an ammeter 37 as in Fig. 1, and the speed of the compressor-turbine assembly is sensed by a tachometer 75. The control system comprises four switches 40, 41, 42, 43, three summation points 50, 60, 84 and two integrators 52, 62. In the position shown a signal from the integrator 52 is passed to the point 50 to which is added a set signal 51, the difference being communicated through switch 41 to the integrator. The signal from the integrator is also passed to the second terminal of the switch 40, the switch being connected to a zero set point which signal is communicated to the actuator 35 of the water valve 31 so that no water is supplied to the combustion gas line 10. A speed signal from the tachometer 75 is compared at point 74 with a set speed signal 76, the resulting signal passing through line 77 to the second terminal of the switch 41. Upon loss of load on the generator 15 sensed by the ammeter 37, the switches 40, 41 are moved to the second position so that the speed error signal in line 77 is communicated through switch 41 to the integrator and so through switch 40 to the actuator 35 which causes the valve 31 to open so allowing water to pass to the combustion gas line 10. The switch 43 in the position shown passes the signal 70 for the rate of supply of fuel to the actuator 66 which sets the fuel valve 12 correspondingly. The switch 42 passes a signal from the integrator 62 and a set value signal 61 to the summation point 60 back to the integrator. Upon loss of load of the generator, the switches 42, 43 move to the second position so that a signal from the point 84 is passed through switch 42 to the integrator 62 and so through switch 43 to the actuator 66, whereby the flow of fuel is controlled.